The internet enables us to share information faster than ever before, but if you want to know what really drives online popularity, look no further than the 56 seconds of raw emotional drama that is "Charlie Bit My Finger — Again!"

Al Gore may have invented the internet* in the hope that humans would use it to spread knowledge, but instead it's mainly used to share YouTube videos (and porn — lots of porn). Jonah Berger, an assistant professor at the University of Pennsylvania's Wharton School, says that's because our bodies mirror the reactions we see on screen, and we're more likely to share information when we're in a heightened state of arousal. The Wall Street Journalreports:

When he had subjects jog in place for 60 seconds-Mr. Berger wanted to trigger the symptoms of arousal directly-the number of people who emailed a news article to their friends more than doubled. He also boosted levels of "social transmission" by showing his subjects frightening and funny videos first. "Levels of arousal spill over," Mr. Berger says. "When people are aroused, they are much more likely to pass on information."

In previous research, Berger looked at 7,500 articles that appeared on the New York Times' "Most Emailed" list and determined that an article that provoked an emotional reaction was far more likely to end up on the list than some practical guide to spending 36 hours in Quito, Equador. Berger says this is linked to our drive to bond with others by sharing emotions. So if your goal is to create a viral hit, don't bother with useful content. All people really want to do is share in the joy of watching parents exploit their kids' trauma for the amusement of others.